1. Field of the Invention
This invention relates to the determination of critical film thickness of compound semiconductor layers and a method for manufacturing semiconductor devices using the method of determination.
2. Description of Related Art
In an incomplete lattice matching system, layers with thickness thinner than critical film thickness and an element which includes strain is formed. To obtain emitting wavelength required for optical elements, the mixed crystal ratio of an active layer and thickness of an active layer are changed. However, to improve the basic performance, carrier or light is confined strongly, or a thin film containing internal strain is used for an active layer or a layer near an active layer to suppress the propagation of defects and dislocations.
However, conventionally dislocation is checked using an electron microscopy to obtain the critical film thickness, the checking work takes much manpower, thus it has been difficult to manufacture optical elements under the optimal condition and semiconductor elements with excellent performance have not been obtained.